Electrically controlled terahertz modulator with deep modulation and slow wave effect via a HEMT integrated metasurface.

Slow wave and localized field are conducive to terahertz (THz) modulators with deep and fast modulation. Here we propose an electrically controlled THz modulator with slow wave effect and localized field composed of a high electron mobility transistor (HEMT) integrated metasurface. Unlike previously proposed schemes to realize slow wave effect electrically, this proposal controls the resonant modes directly through HEMT switches instead of the surrounding materials, leading to a modulation depth of 96% and a group delay of 10.4ps. The confined electric field where HEMT is embedded, and the slow wave effect, work together to pave a new mechanism for THz modulators with high performance.

A Case Series of Children With 2019 Novel Coronavirus Infection: Clinical and Epidemiological Features.

We first described the 2019 novel coronavirus infection in 10 children occurring in areas other than Wuhan. The coronavirus diseases in children are usually mild and epidemiological exposure is a key clue to recognize pediatric case. Prolonged virus shedding is observed in respiratory tract and feces at the convalescent stage.

Polarization-independent and angle-insensitive broadband absorber with a target-patterned graphene layer in the terahertz regime.

We propose a broadband tunable metamaterial absorber with near-unity absorption in the terahertz regime based on a target-patterned graphene sheet. Due to gradient diameter modulation of the graphene sheet and circular symmetry of the unit cell, broadband and polarization-independent properties are achieved in the absorber. A full-wave numerical simulation is performed, and the results show that the absorber's bandwidth of 90% terahertz absorption reaches 1.57 THz with a central frequency of 1.83 THz under normal incidence. At oblique incidence, the broadband absorption of the absorber remains more than 75% over a wide incidence angles up to 60°for the transverse electric (TE) mode and 75°for the transverse magnetic (TM) mode. Furthermore, tunable property is implemented and the peak absorption of the absorber can be tuned from 19% to near 100% by changing the Fermi energy of the graphene sheet from 0 to 0.9 eV via electrostatic doping. The absorber is scalable to the infrared and visible frequencies, which could be used as tunable sensors, filters and photovoltaic devices.

Carboxylated Agarose (CA)-Silk Fibroin (SF) Dual Confluent Matrices Containing Oriented Hydroxyapatite (HA) Crystals: Biomimetic Organic/Inorganic Composites for Tibia Repair.

By in situ combining the dual cross-linking matrices of the carboxylated agarose (CA) and the silk fibroin (SF) with the hydroxyapatite (HA) crystals, the CA-SF/HA composites with optimal physicochemical and biological properties were obtained, which were designed to meet the clinical needs of load-bearing bone repair. With the synergistic modulation of the dual organic matrices, the HA nanoparticles presented sheet and rod morphologies due to the preferred orientation, which successfully simulated the biomineralization in nature. The chemical reactivity of the native agarose (NA) was significantly enhanced via carboxylation, and the CA exhibited higher thermal stability than the NA. In the presence of SF, the composites showed optimal mechanical properties that could meet the standard of bone repair. The degradation of the composites in the presence of CA and SF was significantly delayed such that the degradation rate of the implant could satisfy the growth rate of the newly formed bone tissue. The in vitro tests confirmed that the CA-SF/HA composite scaffolds enabled the MG63 cells to proliferate and differentiate well, and the CA/HA composite presented greater capability of promoting the cell behaviors than the NA/HA composite. After 24 days of implantation, newly formed bone was observed at the tibia defect site and around the implant. Extensive osteogenesis was presented in the rats treated with the CA-SF/HA composites. In general, the CA-SF/HA composites prepared in this work had the great potential to be applied for repairing large bone defects.

A novel fluorescence platform for specific detection of tetracycline antibiotics based on [MQDA-Eu3+] system.

Tetracycline antibiotics (TCs) are extensively used in clinical medicine, animal husbandry, and aquaculture because of their cost-effectiveness and high antibacterial efficacy. However, the presence of TCs residues in the environment poses risks to humans. In this study, an inner filter effect (IFE) fluorescent probe, 2,2'-(ethane-1,2-diylbis((2-((2-methylquinolin-8-yl)amino)-2-oxoethyl)azanediyl))diacetic acid (MQDA), was developed for the rapid detection of Eu3+ within 30 s. And its complex [MQDA-Eu3+] was successfully used for the detection of TCs. Upon coordination of a carboxyl of MQDA with Eu3+ to form a [MQDA-Eu3+] complex, the carboxyl served as an antenna ligand for the effective detection of Eu3+ to intensify the emission intensity of MQDA via "antenna effect", the process was the energy absorbed by TCs via UV excitation was effectively transferred to Eu3+. Fluorescence quenching of the [MQDA-Eu3+] complex was caused by the IFE in multicolor fluorescence systems. The limits of detection of [MQDA-Eu3+] for oxytetracycline, chlorotetracycline hydrochloride, and tetracycline were 0.80, 0.93, and 1.7 µM in DMSO/HEPES (7:3, v/v, pH = 7.0), respectively. [MQDA-Eu3+] demonstrated sensitive detection of TCs in environmental and food samples with satisfactory recoveries and exhibited excellent imaging capabilities for TCs in living cells and zebrafish with low cytotoxicity. The proposed approach demonstrated considerable potential for the quantitative detection of TCs.

Diagnostic Value of Nutritional Risk Index and Other Indices for Predicting Sarcopenia in the Middle-Aged and Elderly Population of China Without Cancer: A ROC Curve Analysis.

Background: Emerging evidence suggests that systemic inflammatory and nutritional biomarkers, along with derived indices, could serve as predictors for sarcopenia in cancer population. This study aimed to compare these predictors, focusing on the nutritional risk index (NRI) and evaluate its diagnostic value, for sarcopenic patients without cancer. Methods: This cross-sectional retrospective study included 1674 participants. Sarcopenia is defined by skeletal muscle mass index (SMI). Laboratory data reflected the values of systemic inflammatory and nutritional biomarkers, from which the derived indices were calculated. Multiple logistic regression analysis, ROC curve analysis, and the Youden index were utilized to assess the association between these markers and sarcopenia and determine the cutoff value for predicting sarcopenia. Results: Among all participants (1110 men and 564 women, mean age 61.97 ± 9.83 years), 398 individuals were diagnosed with sarcopenia, indicating a prevalence of 23.78% in China's middle-aged and elderly population without cancer. Logistic regression analysis revealed significant associations between all biomarkers and derived indices with sarcopenia. Following adjustment for potential confounders, lower NRI values were significantly associated with a higher incidence of sarcopenia. For sarcopenia diagnosis, the area under the curve (AUC) for NRI was 0.769 ([95% CI, 0.742, 0.796], P < 0.001), with a cutoff value of 106.016, sensitivity of 75.6% and specificity of 66.1%. NRI demonstrated greater predictive advantage for sarcopenia incidence in men compared to women. Conclusion: A lower NRI value was associated with a higher prevalence of sarcopenia. NRI shows promise for early, rapid, and effective sarcopenia screening, particularly in China's middle-aged and elderly male population without cancer.

Reshaping the Diversity of Oxidized Polyquinane Sesquiterpenoids by Cytochrome P450s.

Polyquinane sesquiterpenoids (PQSTs) are complex compounds with two or three fused cabocyclopentane ring systems, and the biocatalysts for direct C-H bond oxidation on these scaffolds have rarely been discovered. In this study, we discovered two versatile fungal CYP450s capable of performing diverse oxidations on seven PQST scaffolds, resulting in the generation of 20 unique products. Our findings significantly expand the diversity of oxidized PQST scaffolds and provide important biocatalysts for the selective oxidation of inert carbons of terpenoids in future research.

Dynamic monitoring of serum specific tumor markers predicts the response to PD-1 blockade and prognosis of patients with malignant tumors.

BACKGROUND: Programmed cell death protein 1 (PD-1) blockade is a major advance in the treatment of malignancies, but there remain many problems in efficacy evaluation. The aim of this study was to determine whether dynamic monitoring of serum specific tumor markers (SSTMs) could predict the response to PD-1 blockade and prognosis in patients with malignancies. METHODS: The dynamic changes in SSTMs in 27 patients between January 1, 2018 and July 31, 2019 were analyzed retrospectively. The association between the SSTM response and the radiological response was evaluated using the χ2 test and Spearman's correlation analysis. Kaplan-Meier estimates and the log rank test were used to explore the correlation of SSTM dynamics with progression-free survival (PFS) and overall survival (OS). RESULTS: In this study, 85.3% of patients with malignant tumors had detectable SSTM. According to the changes of SSTM within the first 12 weeks of treatment, the patients were divided into a tumor marker increased group and a tumor marker decreased group. The change in SSTM was strongly associated with the change in target lesions (χ2=15.326, P≤0.001), and there was a positive correlation between them (Pearson Correlation r=0.727, P<0.0001). Patients with SSTM reduction had a significantly longer median OS (417 days) when compared with patients with SSTM elevation (median OS, 235 days; log rank χ2=6.323, P=0.012). The PFS in the SSTM reduction group (median PFS, not reached) was significantly longer than that in the elevation group (127 days; log rank χ2=8.843, P=0.003). In the study, one patient showed pseudoprogression and one showed a delayed response in the initial stage of PD-1 blockade. The diameter of the target lesions increased according to the Reaction Evaluation Criteria in Solid Tumor criteria, but the symptoms of discomfort were relieved significantly, and the SSTMs continued to decline dramatically. CONCLUSIONS: Dynamic monitoring of SSTMs can be used as a necessary supplement to imaging examination to evaluate the response to PD-1 blockade and predict the prognosis of patients with malignancies; it may also be helpful for clinical judgment of pseudoprogression and delayed response.

Development and Validation of a Nomogram for Preoperative Prediction of Lymph Node Metastasis in Lung Adenocarcinoma Based on Radiomics Signature and Deep Learning Signature.

BACKGROUND AND PURPOSE: The preoperative LN (lymph node) status of patients with LUAD (lung adenocarcinoma) is a key factor for determining if systemic nodal dissection is required, which is usually confirmed after surgery. This study aimed to develop and validate a nomogram for preoperative prediction of LN metastasis in LUAD based on a radiomics signature and deep learning signature. MATERIALS AND METHODS: This retrospective study included a training cohort of 200 patients, an internal validation cohort of 40 patients, and an external validation cohort of 60 patients. Radiomics features were extracted from conventional CT (computed tomography) images. T-test and Extra-trees were performed for feature selection, and the selected features were combined using logistic regression to build the radiomics signature. The features and weights of the last fully connected layer of a CNN (convolutional neural network) were combined to obtain a deep learning signature. By incorporating clinical risk factors, the prediction model was developed using a multivariable logistic regression analysis, based on which the nomogram was developed. The calibration, discrimination and clinical values of the nomogram were evaluated. RESULTS: Multivariate logistic regression analysis showed that the radiomics signature, deep learning signature, and CT-reported LN status were independent predictors. The prediction model developed by all the independent predictors showed good discrimination (C-index, 0.820; 95% CI, 0.762 to 0.879) and calibration (Hosmer-Lemeshow test, P=0.193) capabilities for the training cohort. Additionally, the model achieved satisfactory discrimination (C-index, 0.861; 95% CI, 0.769 to 0.954) and calibration (Hosmer-Lemeshow test, P=0.775) when applied to the external validation cohort. An analysis of the decision curve showed that the nomogram had potential for clinical application. CONCLUSIONS: This study presents a prediction model based on radiomics signature, deep learning signature, and CT-reported LN status that can be used to predict preoperative LN metastasis in patients with LUAD.

Unsteady-state direct partial oxidation of methane to synthesis gas in a fixed-bed reactor using AFeO3 (A = La, Nd, Eu) perovskite-type oxides as oxygen storage.

Direct partial oxidation of methane to synthesis gas on AFeO(3) (A = La, Nd, Eu) oxides by a novel sequential redox cyclic reaction in the absence of gaseous oxygen was investigated over a fixed-bed reactor. These oxides were prepared by the sol-gel method and characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. XRD analysis showed that all AFeO(3) (A = La, Nd, Eu) oxides, calcined at 1173 K, are single-phase perovskites. The CH(4)-TPSR/MS and continuous reaction experiments indicated that the AFeO(3) (A = La, Nd, Eu) oxides provide mostly oxygen species, as the sole oxidant originated from lattice oxygen instead of gaseous oxygen, which can oxidize CH(4) to synthesis gas with high selectivity in the absence of gaseous oxygen. In terms of material economics and the amount of oxygen species for synthesis gas formation, the LaFeO(3) sample exhibits the best performance among these tested AFeO(3) oxides for synthesis gas production. The pulse experiments at different temperatures showed that the rate of oxygen migration during the CH(4) reaction with LaFeO(3) is strongly affected by the reaction temperature, and increases with rising temperature, which is favorable to much more CH(4) selective oxidation at high temperature. The two types of oxygen species are identified by experiments of continuous reactions and pulses, and confirmed by XPS. Methane can be converted selectively to synthesis gas by consumption of lattice oxygen, and general carbonaceous deposits on the catalyst surface do not occur under the appropriate reaction conditions by sequential redox cycles. The performance of selective oxidation of CH(4) to synthesis gas can be recovered by reoxidation using gaseous molecular oxygen; the LaFeO(3) oxide maintains relatively high catalytic activity and structural stability in redox atmospheres.

Hydrogen production from a combination of the water-gas shift and redox cycle process of methane partial oxidation via lattice oxygen over LaFeO3 perovskite catalyst.

A redox cycle process, in which CH4 and air are periodically brought into contact with a solid oxide packed in a fixed-bed reactor, combined with the water-gas shift (WGS) reaction, is proposed for hydrogen production. The sole oxidant for partial oxidation of methane (POM) is found to be lattice oxygen instead of gaseous oxygen. A perovskite-type LaFeO3 oxide was prepared by a sol-gel method and employed as an oxygen storage material in this process. The results indicate that, under appropriate reaction conditions, methane can be oxidized to CO and H2 by the lattice oxygen of LaFeO3 perovskite oxide with a selectivity higher than 95% and the consumed lattice oxygen can be replenished in a reoxidation procedure by a redox operation. It is suggested that the POM to H2/CO by using the lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable. The LaFeO3 perovskite oxide maintained relatively high catalytic activity and structural stability, while the carbonaceous deposits, which come from the dissociation of CH4 in the pulse reaction, occurred due to the low migration rate of lattice oxygen from the bulk toward the surface. A new dissociation-oxidation mechanism for this POM without gaseous oxygen is proposed based on the transient responses of the products checked at different surface states via both pulse reaction and switch reaction over the LaFeO3 catalyst. In the absence of gaseous-phase oxygen, the rate-determining step of methane conversion is the migration rate of lattice oxygen, but the process can be carried out in optimized cycles. The product distribution for POM over LaFeO3 catalyst in the absence of gaseous oxygen was determined by the concentration of surface oxygen, which is relevant with the migration rate of lattice oxygen from the bulk toward the surface. This process of hydrogen production via selective oxidation of methane by lattice oxygen is better in avoiding the deep oxidation (to CO2) and enhancing the selectivity. Therefore, this new route is superior to general POM in stability (resistance to carbonaceous deposition), safety (effectively avoiding accidental explosion), ease of operation and optimization, and low cost (making use of air not oxygen).

Observation of the Zero Doppler Effect.

The normal Doppler effect has well-established applications in many areas of science and technology. Recently, a few experimental demonstrations of the inverse Doppler effect have begun to appear in negative-index metamaterials. Here we report an experimental observation of the zero Doppler effect, that is, no frequency shift irrespective of the relative motion between the wave signal source and the detector in a zero-index metamaterial. This unique phenomenon, accompanied by the normal and inverse Doppler effects, is generated by reflecting a wave from a moving discontinuity in a composite right/left-handed transmission line loaded with varactors when operating in the near zero-index passband, or the right/left-handed passband. This work has revealed a complete picture of the Doppler effect in metamaterials and may lead to potential applications in electromagnetic wave related metrology.

Biomineralization-inspired synthesis of chitosan/hydroxyapatite biocomposites based on a novel bilayer rate-controlling model.

In order to prepare sophisticated biomaterials using a biomimetic approach, a deeper understanding of biomineralization is needed. Of particular importance is the control and regulation of the mineralization process. In this study, a novel bilayer rate-controlling model was designed to investigate the factors potentially influencing mineralization. In the absence of a rate-controlling layer, nano-scale hydroxyapatite (HA) crystallites exhibited a spherical morphology, whereas, in the presence of a rate-controlling layer, HA crystallites were homogeneously dispersed and spindle-like in structure. The mineralization rate had a significant effect on controlling the morphology of crystals. Furthermore, in vitro tests demonstrated that the reaction layer containing spindle-like HA crystallites possessed superior biological properties. These results suggest that a slow mineralization rate is required for controlling the morphology of inorganic crystallites, and consumption by the rate-controlling layer ensured that the ammonia concentration remained low. This study demonstrates that a biomimetic approach can be used to prepare novel biomaterials containing HA crystallites that have different morphologies and biological properties.

Realizing Tunable Inverse and Normal Doppler Shifts in Reconfigurable RF Metamaterials.

The Doppler effect has well-established applications in astronomy, medicine, radar and metrology. Recently, a number of experimental demonstrations of the inverse Doppler effect have begun to appear. However, the inverse Doppler effect has never been observed on an electronically reconfigurable system with an external electromagnetic wave source at radio frequencies (RF) in experiment. Here we demonstrate an experimental observation of the inverse Doppler shift on an electronically reconfigurable RF metamaterial structure, which can exhibit anomalous dispersion, normal dispersion or a stop band, depending on an applied bias voltage. Either inverse or normal Doppler shift is realized by injecting an external RF signal into the electronically reconfigurable metamaterial, on which an electronically controllable moving reflective boundary is formed. The effective velocity of this boundary and the resulting frequency shift can be tuned over a wide range by a digital switching circuit. This work is expected to open up possibilities in applying the inverse Doppler effect in wireless communications, radar and satellite navigation.